Hammond 1140-DB-A 200K to 1.5K Direct Box Transformer, 12:1 Ratio

The 1140-DB-A is the direct box transformer in the 1140 Series of studio grade impedance matching transformers. It converts an unbalanced line level signal into a balanced microphone level output, which the manufacturer describes as ideal for feeding long cables with minimal high frequency losses. Live sound engineers, studio builders and DI box designers are the natural buyers.

The impedance ratio is 200K:1.5K with a rated 12:1 turns ratio (11.54:1 typical on the drawing). Rated performance is +22 dBu maximum input at 20 Hz, 0.02% THD at 20 Hz and a frequency response of -0.07 dB at 20 Hz and -0.07 dB at 20 kHz. Typical drawing figures include 140K primary input impedance and 150 ohm secondary output impedance at 1 kHz, 70 dB common mode rejection at 60 Hz and 60 dB at 3 kHz, and THD of 0.025% at 1 kHz and 0.0025% at 20 Hz (-20 dBu).

The core is a nickel alloy, and the windings sit inside a mu metal can with dual shields for excellent shielding. Primary DCR is 4.25 K and secondary DCR 72.0 at 20 °C, dielectric strength is 500 Vrms, and capacitance is 550 pF primary and 480 pF secondary to shield and case.

The 1140-DB-A is a chassis mount part with colour-coded leads: brown and orange for the primary, green and green/yellow for the secondary, grey and grey/white for the shields and violet for the can ground. It is RoHS and REACH compliant, made in Canada and ships at 0.2 lbs (0.09 kg).